Conditional Handover Command Management in 5G Wireless Systems
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Solution Overview
Problem
Current wireless communication systems, particularly 5G NR, face challenges in handover reliability due to rapid serving cell quality degradation and blockage issues, leading to service interruptions and increased handover failure rates.
Innovation Solution
The implementation of Conditional Handover (CHO) technology, which allows User Equipment (UE) to execute handovers to a target base station based on predefined trigger conditions, including the use of measurement IDs and report configurations, while forgoing measurement reports during handover execution and managing CHO command removals through RRC messages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional handover procedures are used, then the system operates with simpler protocols, but handover reliability deteriorates due to rapid serving cell quality degradation and blockage issues
Solution Approach 1:
The patent implements Conditional Handover (CHO) by preparing handover commands in advance and configuring multiple candidate target cells before handover is actually needed. The UE receives CHO commands from the source gNB that include configurations for multiple potential target cells, and can autonomously execute handover to any suitable target when trigger conditions are met, without requiring real-time network intervention. This preliminary preparation resolves the contradiction by enabling reliable handovers under rapid degradation scenarios while managing complexity through pre-configured automation.
Solution Approach 2:
The CHO mechanism enables the UE to autonomously evaluate trigger conditions and select appropriate target cells from pre-configured candidates without continuous network control. The UE independently monitors serving cell quality, compares it against configured thresholds, and executes handover decisions locally when conditions are satisfied. This self-service capability improves handover reliability in blockage scenarios by eliminating network latency in the decision-making process, while the pre-configured nature of CHO keeps complexity manageable.
2Loss of information
If measurement reports are continuously transmitted during handover execution, then the network maintains full visibility of UE measurements, but signaling overhead and processing complexity increase
Solution Approach 1:
The patent extracts the measurement reporting function from the handover execution process during CHO. When a UE executes a CHO command, it forgoes transmitting measurement reports to the source gNB, as the handover decision and execution are already embedded in the pre-configured CHO command. This extraction resolves the contradiction by eliminating unnecessary signaling overhead during handover while maintaining measurement information availability through the autonomous UE evaluation of trigger conditions that were pre-configured with the CHO command.
Solution Approach 2:
The CHO mechanism ensures continuous handover capability by pre-configuring multiple candidate target cells with their respective trigger conditions. The UE continuously monitors serving cell quality against these pre-configured thresholds and can immediately execute handover to any suitable target without interruption or additional signaling. This continuity resolves the contradiction by maintaining measurement information availability through continuous autonomous monitoring while eliminating the complexity of continuous measurement report transmission to the network.
3Adaptability or versatility
If the network manages CHO command removals explicitly through instructions, then the network maintains precise control over UE configurations, but signaling overhead increases
Solution Approach 1:
The patent implements self-service configuration management where the UE autonomously removes CHO commands based on pre-configured leave conditions. When the UE evaluates that a target cell no longer satisfies the trigger conditions (e.g., signal quality falls below a threshold), it automatically removes the corresponding CHO command without requiring explicit network instructions. This self-service mechanism resolves the contradiction by maintaining configuration control flexibility through pre-configured conditions while dramatically reducing signaling overhead by eliminating the need for continuous network-directed configuration management.
4Reliability
If handover execution waits for network confirmation, then the network maintains centralized control, but handover latency increases during rapid quality degradation
Solution Approach 1:
The patent resolves this contradiction by performing preliminary actions where the network pre-configures multiple CHO commands with target cell configurations and trigger conditions before handover is actually needed. The UE receives these pre-configured commands and can immediately execute handover to any suitable target when trigger conditions are met, without waiting for real-time network confirmation. This preliminary preparation enables rapid handover execution during quality degradation while maintaining reliability through pre-validated target cell configurations approved by the network in advance.
Solution Approach 2:
The CHO mechanism enables the UE to autonomously execute handover decisions based on pre-configured trigger conditions without requiring real-time network confirmation. The UE independently monitors serving cell quality, compares it against configured thresholds, and immediately initiates handover to suitable targets when conditions are satisfied. This self-service capability resolves the contradiction by eliminating network confirmation latency while maintaining reliability through the pre-configured nature of CHO commands that were validated by the network during configuration.
Data Source
AI summary
A method performed by a BS for CHO is provided. The method includes transmitting a CHO command to a UE, the CHO command including a CHO command ID and a measurement ID associated with the CHO command ID; causing the UE to execute the CHO command to handover to a target BS when a trigger condition associated with the measurement ID is fulfilled; causing the UE to forgo transmitting the measurement report during the execution of the CHO command despite the UE being configured, via a report configuration associated with the measurement ID, to transmit the measurement report; transmitting, to the UE, a message that causes the UE to remove the CHO command; and after transmitting the message to the UE, determining that the report configuration is removed by the UE without transmitting, to the UE, an instruction to remove the report configuration.